lO 



some cases the cotton plants upon which the worms were feeding 

 were thoroughly drenched with active yeast. In one instance 

 a number of the larvae were placed in a tin box and drenched for 

 twenty-four hours with yeast ; after this the surplus yeast was 

 drained off and the larvae kept in the same box and fed for a 

 week without showing any symptoms of disease. They were 

 then sent to the department at Washington, where they arrived 

 safely, and never gave those receiving them cause to suppose that 

 they had been thus treated. Similar results attended all the 

 experiments tried by Mr. Trelease, and he was led to the conclu- 

 sion that the proposed remedy could not be utilized for the 

 destruction of the cotton caterpillar. 



On the other hand, Dr. Hagen mentions some experiments made 

 last summer by Mr. J. H. Burns, of Shelter Island, N. Y., on the 

 potato beetle, as being successful. A quantity of beetles was 

 divided into two parcels, one of which was sprinkled on succes- 

 sive days with dilute yeast. 



On the eighth day those sprinkled began to die, and on the 

 thirteenth all were dead. Of the unsprinkled parcel only a few 

 had died. That this experiment is decisive can hardly be claimed, 

 as it is probable that some other substance, as for insta;ice, dilute 

 flour paste, which would favor the growth of fungi, might have 

 had the same effect as the yeast. At all events, the experiment 

 must necessarily be tried upon the beetles as they are found in 

 their natural state infesting the potato plants, before any definite 

 conclusion can be drawn. 



It is true that Dr. Hagen found spores in quantity in the large 

 sinus of the wing of the dead beetles which had been sprinkled, 

 but it does not appear that these were in any way directly con- 

 nected with the'Torulae of the yeast. It should also be noted that 

 Dr. Hagen states in the May number of the Canadian Entomolo- 

 gist, for 1880, that he has recently received a letter from Germany, 

 giving an account of the use of the diluted (compressed) yeast 

 upon aphides in a green-house, " which was successful to an ex- 

 ceeding degree ; " but no details in regard to the experiment are 

 given. 



Possibly the kind of yeast used may make a great difference in 

 the result, although it should be remembered that three different 

 kinds have been used in the experiments detailed in this paper. 



It is also worthy of note that yeast, as suggested by Prof. 



